feat(quota): add Claude Code and Devin subscription quota probes

[SousekiL]

What changed

Adds two more quota-detection sources on top of the QuotaManager from #845 (this PR stacks on top of #845 and includes its commits; the binding-window display now lives in #845 itself; recommend merging this PR after #845 lands, or having @ana52070 fold these two providers directly into #845):

• Claude Code: reads the OAuth credentials Claude Code itself saves after login (the macOS Keychain entry Claude Code-credentials, or <CLAUDE_CONFIG_DIR|~/.claude>/.credentials.json on other platforms), and calls the same endpoint used by Claude Code's /usage command, https://api.anthropic.com/api/oauth/usage (with anthropic-beta: oauth-2025-04-20), mapping the five_hour / seven_day utilization to the 5-hour and weekly windows, and mapping subscriptionType to the plan name. Shows a clear message instead of a raw HTTP error when the login has expired.
• Devin CLI: reads windsurf_api_key and api_server_url from ~/.local/share/devin/credentials.toml (supports XDG_DATA_HOME), and calls the same Connect RPC that Devin CLI itself uses, exa.seat_management_pb.SeatManagementService/GetUserStatus, taking daily / weekly quota remaining percentage, reset time, plan name, and ACU usage from PlanStatus (ACU is appended after the plan name in the form 12.2 / 150 ACU). Both the built-in devin id and the user-registered custom:devin id point to the same account and the same detection.
• Frontend SUPPORTED_AGENTS gains claude_code, devin, custom:devin; reuses feat(quota): 接入 Codex 与 Antigravity 实时额度探测与监控 #845's badge and popover, no new UI.
• Consistent with feat(quota): 接入 Codex 与 Antigravity 实时额度探测与监控 #845: credentials are only sent to their issuer, never persisted to disk, never forwarded elsewhere.

Testing

• cargo test --no-default-features --bin codeg-server --lib quota → 27 unit tests pass (6 new: payload parsing for both sides, missing-field tolerance, credential validation, camelCase / snake_case compatibility).
• composer-quota-badge.test.tsx → 9 pass (2 new cases for Claude and custom:devin; the original "unsupported agent" case now uses gemini).
• tsc --noEmit passes.
• Note: the response fields for both remote endpoints were written based on the definitions found in the Claude Code / Devin CLI binaries, with parsing tolerant of both camelCase and snake_case. Verification against my own live accounts is still in progress; I'll follow up with fixes on this PR if any fields turn out to differ.

Assisted with Claude Code

[ana52070]

感谢补充 Claude Code 和 Devin 的额度探测支持！
我倾向于保持 #845 先完成 QuotaManager + Codex / Antigravity 的基础实现，等 #845 合并后，再让 #850 基于最新 main 继续合入 Claude Code / Devin，这样 review 和提交历史会更清晰一些。
如果维护者更希望一次性处理，也可以将这两个 provider 一并收进 #845，我这边可以配合调整。

[SousekiL]

Agreed — #845 first. I've marked this as draft and will rebase onto main once #845 lands.

One thing for #845 itself: the badge always prefers the 5-hour window, but ChatGPT Pro reports one that stays ~100% while the weekly budget drains, so Pro users see a meaningless "5h" figure. My last commit here (fix(quota): badge shows the binding window…) shows whichever window has less left. It touches your badge code, so it may fit better in #845 — feel free to take it.

[ana52070]

Thanks, that makes sense. I'll bring the binding-window badge fix into #845. Appreciate you catching this!

[ana52070]

The binding-window badge fix has been committed and pushed to #845 (26692b3). Thanks again for the spot and suggestion!

[SousekiL]

Nice, thanks for the quick fix!